DB operations and java.lang.RuntimeException: No columns in table: X

Hi people This is my first post here at saloon javaranch forums. I have had a problem for a couple of days now and I can't find a solutions to it. I'm trying to develop the user management section of a webapplication. I have a page for adding users and a page for view users. In the view page I use a table which is binded to a Cached Row Set through a data provider called userDataProvider. I have added a column of type checkbox to the table and command buttons for deleting, updating and so on. Everything seemed to be working fine before, but not any more. I do the update operation through JDBC and it works fine. Deleting and insertion is done through the data provider.

I think the problems accured after I had altered the db table a couple of time (added and removed columns), but I'm not sure. Now I cann't commit add nor delete rows. I get the following message: